Surveillance for Possible Chemical Emergencies

There is an obvious need for health-care providers and public health officials to be alert for patients in their communities who have signs and symptoms consistent with chemical exposures. State and local health departments should educate health-care providers to recognize unusual illnesses that might indicate release of a chemical agent.

A covert release of a chemical agent might not be identified easily for at least five reasons:

Symptoms of exposure to some chemical agents might be similar to those of common disease;

Immediate symptoms of certain chemical exposures might be nonexistent or mild despite the risk for long-term effects (e.g., neurocognitive impairment from dimethyl mercury, teratogenicity from isotretinoin, or cancer from aflatoxin);

Exposure to contaminated food, water, or consumer products might result in reports of illness to health-care providers over a long period and in various locations;

Persons exposed to two or more agents might have symptoms not suggestive of any one chemical agent (i.e., a mixed clinical presentation); and

Health-care providers might be less familiar with clinical presentations suggesting exposure to chemical agents than they are with illnesses that are treated frequently.

Epidemiologic clues that might suggest the covert release of a chemical agent include:

An unusual increase in the number of patients seeking care for potential chemical-release--related illness;

Unexplained deaths among young or healthy persons;

Emission of unexplained odors by patients;

Clusters of illness in persons who have common characteristics, such as drinking water from the same source;

Rapid onset of symptoms after an exposure to a potentially contaminated medium (e.g., paresthesias and vomiting within minutes of eating a meal);

Unexplained death of plants, fish, or animals (domestic or wild); and

A syndrome (i.e., a constellation of clinical signs and symptoms in patients) suggesting a disease associated commonly with a known chemical exposure (e.g., neurologic signs or pinpoint pupils in eyes of patients with a gastroenteritis-like syndrome or acidosis in patients with altered mental status).

CDC is collaborating with the American Association of Poison Control Centers to use its Toxic Exposure Surveillance System to identify index cases, evolving patterns, or emerging clusters of hazardous exposures. Identification of early markers for chemical releases (e.g., characteristic symptom complexes, temporal and regional increases in hospitalizations, or sudden increases in case frequency or severity) will enable public health authorities to respond quickly and appropriately to an intentional chemical release.

Providing information or reminders to health-care providers and clinical laboratories;

Encouraging reporting of acute poisonings to local poison control centers, which can guide patient management and facilitate notification of the proper health agencies, and to the local or state health department;

Initiating surveillance for incidents that potentially involve the covert release of a chemical agent;

Implementing the capacity to receive and investigate any report of such an event;

Implementing appropriate protocols, including potentially accessing the Laboratory Response Network for Bioterrorism, to collect and transport specimens and to store them appropriately before laboratory analysis;

Reporting immediately to CDC and local law enforcement if the results of an investigation suggest the intentional release of a chemical agent; and

How To Do Population Follow-up

Persons potentially or actually exposed to chemicals during an emergency event should be considered for long-term follow-up depending on the chemical and its effects. To see chemical specific recommendations, click on the chemical category below.

Tracking may be required for many years, as late chemical effects may not appear for decades.

Within HHS, CDC has been given the responsibility for population monitoring after a mass casualty event. Their documents provide comprehensive guidance.

Delayed Effects: When the chemical has not been identified, the patient should be observed for an extended period or admitted to the hospital.

Patient Release: Asymptomatic patients who have minimal exposure, normal initial examinations, and no signs of toxicity after 6 to 8 hours of observation may be discharged with instructions to seek medical care promptly if symptoms develop.

Follow-up: Provide the patient with follow-up instructions to return to the emergency department or a private physician to reevaluate initial findings. Patients who have corneal injuries should be reexamined within 24 hours.

Additional Information

Data on exposed individuals is usually acquired after the event. This can come from reconstruction of the events, environmental monitoring, and individual reports.

Describing long term health effects becomes problematic for several reasons: deviations in exposure time in the exposed population, background environmental exposure, psychological trauma, exposed population size, and even recognition time that a chemical event is occurring, etc.

After the event, the focus shifts from acute care to long term monitoring to detect delayed effects, and there is a need for follow up with those exposed.

First responders can be the hardest of the exposed to locate and follow up with, as others in the area can be located through work, residential, or school records.